In wireless communication systems, for a given bandwidth, it is desirable to maximize capacity. To maximize capacity, it is known to use multiple antenna techniques such as spatial division multiple access (SDMA), wherein two or more spatially separated mobile stations share the same radio resource. The base station allocates the same radio resource to the mobile stations and employs different effective antenna patterns to transmit the data for each of the mobile stations. Such techniques increase the spectral efficiency of the wireless communication system.
The allocation of radio resources to the mobile stations has a corresponding control channel overhead. If this overhead is not carefully managed, the overhead becomes prohibitively large and limits the capacity of the wireless communication system. This is particularly true for applications, such as voice over internet protocol (VoIP), that require the periodic delivery of small packets.
It is known to use group scheduling to minimize the control channel overhead associated with the delivery of VoIP packets. In group scheduling, a group of mobile stations monitor a shared control channel to determine their respective allocation from a set of shared radio resources, wherein the shared control channel typically contains a bitmap comprising at least one bit for each mobile station. The mobile stations monitor their respective bit of the bitmap to determine if one of the shared radio resources have been allocated by the base station, and determine which of the shared radio resources have been allocated based on the number of mobile stations, with smaller bit positions in the bitmap, that have been allocated a radio resource.
Unfortunately, this group scheduling scheme does not currently handle multiple mobile stations sharing the same radio resource, which occurs for SDMA systems. Thus, there is a need for increasing the number of VoIP users by using spectrally efficient techniques such as SDMA, while efficiently controlling the control channel overhead using group scheduling.